Hi Group, Didn't find much time lastly to contribute, but this topic always triggers something inside....
Do not forget that using such a system only the near field is found, in the orientation the probe determines. In general this has not much to do with the actual 3 or 10 meter emission. By performing relative measurements however, one gets a decent impression in terms of reducing or increasing values relative to a previous IDENTICAL measurement. The probe orientation as well as the distance MUST be well reproduced and the test should be repeated with several orientations of the probe. As an electric field probe (ideally) does not detect magnetic field and vice versa and both contribute to the total emitted radiation, a test in several directions and several operating modes should be conducted with both type of probes. One should also consider probing a PCB from 6 sides, as emission does not have to be maximal in the orthogonal direction of the top side of your PCB. If you're still enthiousiastic about such a project, consider buying a standard bi-conical antenna and create a 3m site on your parking using chicken mesh wire on the floor. I am sure you will get faster and more consistent results then using an XY table and close field probes. EMC is all about measurements in the far field of a source, both in terms of wavelength ( > lambda/3 ) and geometrically relative to the EUT. Regards, Gert Gremmen, (Ing) ce-test, qualified testing =============================================== Web presence http://www.cetest.nl CE-shop http://www.cetest.nl/ce_shop.htm /-/ Compliance testing is our core business /-/ =============================================== >>-----Original Message----- >>From: owner-emc-p...@majordomo.ieee.org >>[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of >>brent.dew...@us.datex-ohmeda.com >>Sent: Wednesday, August 08, 2001 10:03 PM >>To: emc-p...@majordomo.ieee.org >>Subject: board scanning on the cheap (sort of) >> >> >> >>With all this talk about visualization, I thought I'd toss in my bit. >> >>Here at Datex-Ohmeda we have a small NC mill sometimes used by the R&D >>group to make small prototype parts, but it often sits idle. Since I have >>a spectrum analyzer and a variety of small dimension H and E field probes >>I've built, I thought it would be interesting to build the >>equivalent of an >>EMScan. The control program is being written in LabVIEW and is coming >>along pretty well. One nice thing about the mill is that I can >>program the >>scan height for any rectangle I define, so tall components can be hopped >>over. When it's all done, I should be able to play a frequency swept >>"movie" of the board on an intensity graph. The cheaper way to do this >>would be to find an older X-Y plotter and skip the height variation. If I >>ever get the beast done, it will be open source to LabVIEW users. >> >>Best regards, >> >>Brent DeWitt >>Datex-Ohmeda >>Louisville, CO >> >> >>------------------------------------------- >>This message is from the IEEE EMC Society Product Safety >>Technical Committee emc-pstc discussion list. >> >>Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ >> >>To cancel your subscription, send mail to: >> majord...@ieee.org >>with the single line: >> unsubscribe emc-pstc >> >>For help, send mail to the list administrators: >> Michael Garretson: pstc_ad...@garretson.org >> Dave Heald davehe...@mediaone.net >> >>For policy questions, send mail to: >> Richard Nute: ri...@ieee.org >> Jim Bacher: j.bac...@ieee.org >> >>All emc-pstc postings are archived and searchable on the web at: >> http://www.rcic.com/ click on "Virtual Conference Hall," >> >>
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